1. Field
The following description relates to a battery management system. The following description also relates to a mechanism for real time correction of ion concentration and Coulomb counting state-of-charge (SOC) in a battery.
2. Description of Related Art
Generally, batteries are vital source of stored energy that is incorporated into a number of systems. Rechargeable lithium-ion (Li-ion) batteries are attractive energy storage systems for portable electronics, electric vehicle (EV) and hybrid-electric vehicles (HEV) because of their high specific energy compared to other electrochemical energy storage devices. In particular, batteries made of lithium metal incorporated into the negative electrode afford exceptionally high specific energy, in Wh/kg, and energy density, in Wh/L, compared to batteries with conventional carbonaceous negative electrodes. Li-ion batteries also exhibit lack of hysteresis and low self-discharge currents, which are issues that are detrimental to the operation of other types of batteries. Accordingly, lithium-ion batteries are a promising option for incorporation into EVs, HEVs and plug-in hybrid electric vehicles (PHEV), as discussed above, because of these advantageous properties.
One requirement for incorporation of batteries including Li-ion batteries into EV/HEV/PHEV systems, as discussed above, is the ability to accurately compute the state-of-charge (SOC) and state-of-health (SOH) of such batteries in real time. This requirement is important because it allows measurement of the battery's ongoing ability to act as a source of power. The SOC may be defined as a percentage which reflects the available energy in a cell compared to the available energy of the cell when fully charged.
The critical task of a battery management system is to estimate the SOC accurately and manage health of the system to provide a robust battery. SOC estimation is challenging since simple methods of predicting SOC, such as Coulomb counting, suffer from increased errors over an increased integration time. These increased errors result from biased current measurements or discretization errors that occur during such measurements.
Further, the Coulomb counting SOC estimation method suffers from various drawbacks including zero predictability, insensitivity to the operating voltage range, and instability at realistic drive cycles. Moreover in the existing Coulomb counting method, fault detection is not integrated with state estimation.